The present invention relates to a process for recovering useable materials from scrap refuse, comprising metals and non-metals, particularly as produced in the scrapping of used automobiles. Usually scrap articles are reduced in size by grinding or shredding and the ferromagnetic components of the scrap material are recovered. The non-ferrous portion of the scrap (comprising non-ferrous metals and non-metals), is separated from the shredded scrap according to the relative specific gravity of the components using an aqueous separating medium. The aqueous separating medium is mixed with the scrap and a first fraction is removed which consists primarily of non-ferrous metals and a second fraction is removed consisting primarily of non-metals, such as rubber, plastics and textile materials commonly used in automobiles. Though this process is particularly adapted to the treatment of scraped automobiles, it is also useful in other types of scrap material including domestic appliances and optionally other household waste materials.
A method for recovering metals contained in discarded cables and cablewaste has been described in German Auslegeschrift No. 1,263,641. According to the procedure there described, the material is ground and subjected to magnetic separation to remove ferrous-containing components. The non-magnetic fraction is separated according to its specific gravity in a float-and-sink apparatus. In this apparatus, the light fraction, primarily the insulation material, is separated from the heavier fraction which contains the non-ferrous metals such as copper, aluminum and lead. The separating medium used is a suspension having a specific gravity of about 2.0. Such a procedure could be adapted for treating the scrap from waste automobiles and similar materials, however, especially in the case of automobiles and other such waste products, it is necessary to precede the float-and-sink treatment by a procedure in which the non-desirable materials, sometimes referred to as "dirt", such as textile remnants, paper or foam rubber and the like, are removed by a separate separating step using a current of running water. The main reason is that such materials have a high absorption capacity for the separating suspension which would lead to loss of the suspension. Such a method is also limited by the fact that it is not particularly suitable for separating particles smaller than about 6 millimeters which occur in virtually every waste material which is separated to remove the valuable components contained therein. In addition to the necessary requirements of the starting scrap material, the recovery of the heavy portion of the scrap and the maintenance of the correct specific gravity of the suspension necessarily requires the use of expensive equipment.
A procedure has now been found in which metals and non-metals may be selectively separated from shredded scrap in a simpler and more direct process than has been previously described. More particularly, the present process does not require a pre-treatment for removal of non-metal parts (dirt) in a water current, is capable of separating particles smaller than 6 millimeters and does not require the use of a high specific gravity separating medium, thereby avoiding the attendant difficulties of using such a medium and expensive equipment therefore.
A characterizing feature of the invention is the use of equipment which is, in itself, already known and wherein the separation of the metals from the non-metals is accomplished according to the various specific gravities of each by means of at least one hydrocyclone. Water is used as a separating medium and, when mixed with shredded scrap, the resulting suspension is separated into a first fraction which is discharged, together with a certain amount of water, at the cyclone apex. A second fraction is discharged, also together with the attendant water, at the cyclone overflow area. Both of the two separated fractions are de-watered and the components recovered therefrom.
An important advantage of such a procedure, as described herein, when using the hydrocyclone and water is that the otherwise extra step of removing textile materials and other non-metals is obviated.
According to the procedure of the invention, by separating the various fractions of the scrap suspension in a hydrocyclone, the specific gravity of the separation achieved may be considerably larger than the specific gravity of the separating medium itself depending, of course, on the dimensions of the cyclone and on the operating conditions therein, so that the use of a heavy medium (that is, having a high specific gravity) and its inherent drawbacks is avoided. It has been found that the presence of particles smaller than 6 millimeters in the material to be separated causes no substantial difficulties in conducting the process.